Muffling device for pneumatic tools of the turbine type



April 23, 1957 J, FANNEN 2,789,652

MUFFLING DEVICE FOR PNEUMATIC TOOLS OF THE TURBINE TYPE.

Filed Nov. 5, 1953 United States Patent '6 i MUFF LING DEVICE FORPNEUMATIC TOOLSOF THE TURBINE .TYPE

John "Fannen, Lotli, Calif.

Application November 5, 1953, Serial No. 390,281

7 Claims. ((1181-36) This inventionrelates to a mufiling device for pneumatic tools and more particularly to a mufiiing device for use with air driven tools of the rotary or turbine type which will silence the exhaust from such tools and at the same time preventthe induction of'foreign matter into the exhaust or discharge openings of such-tools.

When air driven tools of the rotary or turbine type are used, they are generally operated at speeds of from 600 RP. M. to 100,000 R. P. M. and under relatively high air'pressures with the result that the rotary member of the tool acts in the manner of a siren with respect to the air used to drive the same, and there is an attendant whine or noise level which is particularly objectionable both to the user and to other persons in the vicinity or area where the tool is being used. Moreover, when such tools-are used for grinding, sanding, polishing or'drilling operations in which abrasive materials are employed, foreign matter composed of particles of the abrasive agent as well asmaterial-removed has a tendency to settle in the vicinity where the tool is being used and to enter the air discharge ports of the tool, thus causing considerable damage through abrasion tothe-internal mechanism of the tool.

By employment of the present invention and with respect to the foregoing, it has been found that the induction offoreign matter into the working mechanism of the tool can be eliminated and that the noise induced by the air flowing past'the rotary member and through the exhaust ports of the tool can be substantially reduced and the tool so silenced as to be completely unobjectionable by providing a mufiling device of improved type in which the air discharged from'the rotary member is caused to flow through first and second non-resonant chambers which are adapted to receive in series air discharged from the rotary member in the first chamber and to exhaust such discharged air'from the second chamher.

In accordance with the foregoing the present invention contemplates the provision of a mutlling means which may be either constructed in the body of the tool as an integral part thereof, or may under certain conditions be supplied separately as an attachment therefor, and which, in both cases, will be of simple and sturdy construction and economical to manufacture.

More specifically the present invention contemplates the provision of a mufiiing means for use in or with an air driven rotary type tool having a casing, an operating chamber within the casing, an air discharge means from the operating chamber, and a rotary member operable within the operating chamber; such muflling means including a first mufiling chamber adapted to receive .air discharged through the air discharge means from the operating chamber, a second mufliing chamber adaptedto receive in series such discharged air from the first mufiling chamber, and an air discharge port adapted to exhaust such discharged air from the second mufiling chamber.

The first and second mufiiing chambers should be nondamped in the second chamber.

2,789,652 Patented Apr. 23, .1957

resonant with respect to each other and .the second path of discharged air flowing through the second mufiiing chamber from'air inlet to air outlet will be such that vibrations emanating from the first chamber will be Moreover, the air discharge port should'preferably be ofusuch size and so disposed as to partially restrict the flow of discharged air through 'thetool and to cause the air flowing through the discharge port to flow in an angular direction with respect to the direction of *fiow of discharged air entering and flowing through the second mufiling chamber from the first muffling'chamber.

The above as well as other novel features of the-mufiler means according to the present invention will be more readily understood frornithe following description of the accompanying drawings illustrating the invention in accordance with one ofits preferred embodiments, in which drawings:

Figure l is a side view of a mufiier constructed according to the'present' invention and of the type adapted to be used as an attachment with an air driven tool of the kind shown; and showing, a portion of the mufiier and air tool in section;

Figure 2 is a vview incross-section taken along line 2-2 of Figure l; I

Figure 3 is a fragmentary view in cross-section taken along-line 33 ofFigurejl; and 4 Figure 4 is .a fragmentary cross-sectional .view of a modified'ernbodiment of the invention as would ,be viewed along-line 33 of Figural.

Referring to the drawings, .the, invention as presently il-lustratedis'shown as applied to .a pneumatic tool, generally designated as 10, having a motor assembly of con ventional type consisting of a cylinder 11, having inlet ports 12 and outlet ports 13 disposed in-thermanner shown in the circumference thereof, and a vanedrotor or .operating member 14 which is rotatably mounted in the manner shown within the operating chamber 15 of .the cylinder. The operating member 14 is, as is apparent, responsive to the pressure of the air admitted to the operating chamber 15 from the supply passage 16 through the inlet ports 12 and discharged through the outlet ports 13 to drive the working'implement 17, here shown as an abrasive grinding'Whe-el. The flow of air throughthe opcrating chamber 15 may be controlled by a suitable governor, generally designated as 18. A tubular casing or sleeve 19 is disposed in surrounding relation, with respect to the cylinder 11 to form an exhaust chamber 20 around the cylinder in which the air dischargedthrough the outlet ports 13 of the cylinder is permitted to expand, and the casing 19 is provided with longitudinally disposed slots or discharge ports 21 for discharging the air from the exhaust chamber 20 to atmosphere.

In accordance with the present invention, the exhaust chamber 20 serves as the first mufiling chamber of the mufiling means described hereinbefore in which thevdischarged air flowing from the operating chamber 15 of, the tool is received.

Referring now to the-muiiling attachment adapted to be used with a pneumatic tool of the type above described, such attachment comprises a cylindrical member, gen.- erally designated as 30, having a loose fit as at 31 around the casing 19, The interior of the cylindrical member. 30 is cut away intermediate its end portions to providev a tubularportion 32 which cooperateswiththecasing 19 to defineas'ecc-nd expansion or,mufflingchamberfii for the reception of. air discharged from the exhaust chamber 20 of the't ool through the dischargep orts' 21t; As is apparent, thesecondlrnufiling.charnbers33 is dis-1 posed in surrounding relation with respect to the exhaust or first muflling chamber 20 and is adapted to receive in series from the muftling chamber 20 air discharged from the motor assembly. The relative sizes and shapes of the muffiing chambers 20 and 33, respectively, are such that they are not in resonance with respect to each other, so that vibrations emanating from the first mufiling cham. ber 20 will be damped in the second muffiing chamber 33.

An inwardly extending shoulder 34 is provided at the left end of the cylindrical member 30 for fitting substantially in sealing engagement with a corresponding shoulder 35 of the tool, and adjacent to its right end the cylindrical member 30 is provided with a cylindrical portion 36 which fits loosely around an end portion 37 of the casing 19 and cooperates therewith to define a longitudinally extending circumferential air passage 38 from the expansion chamber 33 which acts to slightly restrict the flow of discharged air through the too] without appreciably decreasing the power factor of the tool. Alternatively, as shown in Figure 4, the cylindrical portion 36 may tightly fit the end portion 37 of the tool casing 19, in which case the surface of the cylindrical portion 36 adjacent to the end portion 37 of the tool casing is grooved, as at 38a, in a longitudinal direction so as to provide restricted air passages from the expansion chamber 33.

The right end of the cylindrical member 30 is provided with a neck 39 which is internally threaded, as indicated at 40. As shown in Figures 1 and 3, the neck 39 is provided with a peripheral slot 41 which extends approximately one third the way around the circumference of the neck 39 near its base. A capping member, generally designated as 42, is provided which has a neck 43 externally threaded, as at 44, to fit the internal threads 40 of the neck 39 and, as will beobserved from Figure 1, the capping member 42 fits substantially in sealing engagement with the body of the tool, as at 45, and serves to clamp the mufller firmly in position on the tool without closing ofif the slot 41.

When the cylindrical member 30 and the capping member 42 are securely clamped on the tool as described above, the air discharged from the first muflling or exhaust chamber 20 of the tool through the discharge ports 21 in the casing 19 will first be permitted to expand in the second mufiling chamber 33 in an outward direction and in surrounding relation with respect to the tool casing 19 and will then be caused to flow in a longitudinal direction through the restricting air passage 38 and exhaust opening 41 where it will be discharged to atmosphere in an outward and radial direction. The causing of the air discharged from the tool casing 19 through the discharge ports 21 to be discharged to atmosphere in such manner as described has the effect of dampening the vibrations emanating from the exhaust chamber 20 in the expan-- sion chamber 33 and will so attenuate the noise level of the discharged air as to silence the operation of the tool. Moreover, the muflling of the air discharged from the tool in the manner described will also serve at the same time to prevent the induction or entering of foreign material through the discharge ports into working mecha nism of the tool both during operation and while the tool is lying idle.

While the invention has been specifically illustrated and described with respect to a preferred embodiment thereof of the type which is adapted to be used as an attachment with respect to an air driven rotary type tool of the type described, it is obvious that the muffler attachment may be readily adapted for use with other rotary type tools in which the air discharged from the rotary member of the tool is caused to flow through an exhaust or expansion chamber prior to discharge from the tool and that the novel features of the present invention may also, if desired, be readily incorporated as an integral part of the tool in a simple and economical manner.

What is claimed is:

1. A mutfier for use with pneumatic tOOls of the type described including a tubular casing, an operating chamber having an air discharge means within said casing, an air driven rotary member operable within said casing, an expansion chamber within said casing adapted to receive air discharged through said air discharge means, and an exhaust port adapted to discharge from said casing such discharged air from said expansion chamber; said muffier comprising an outer member having an intermediate portion larger than the casing and adapted to surround said casing and exhaust port in spaced relation with respect thereto, a shoulder portion at one end adapted to engage the body of the tool substantially in sealed relation, a shoulder portion at the other end adapted to loosely surround said casing, said shoulder portions and intermediate portion cooperating to define a mufiiing chamber for air discharged through said exhaust port, air discharge means adapted to exhaust to atmosphere discharged air in said muffling chamber, said discharge means being so disposed in said cylindrical member that the path of the discharged air flowing through said discharge means will be angular with respect to the direction of flow of the air entering said mufiiing chamber through said exhaust port and a neck portion extending from said shoulder portion loosely surrounding said casing; and a capping member engageable with the neck portion of said outer member and cooperating with the body of the tool substantially in sealed relation to clamp said capping member and outer member on the tool.

2. The muflier according to claim 1 wherein the air is discharged from the exhaust chamber in an outward and radial direction through the discharge port in the casing and the air discharge means in the outer member is located in a shoulder portion such that the path of the air exhausted through said discharge means is in a longitudinal direction with respect to said outer member.

3. The mufiler according to claim 1 wherein the air discharge means will restrict the flow of discharged air through the pneumatic tool.

4. A mufiler for use with pneumatic tools of the type described including a tubular casing, an operating chamber having an air discharge means within said casing, an air driven rotary member operable within said casing, an expansion chamber within said casing adapted to receive air discharged through said air discharge means, and an exhaust port adapted to discharge from said casing such discharged air from said expansion chamber: said mufiler comprising a cylindrical member having an intermediate tubular portion of larger diameter than the tubular casing adapted to encircle said tubular casing and discharge ports in spaced relation with respect thereto, a shoulder portion at one end adapted to engage the body of the tool substantially in sealed relation, said shoulder portion and tubular portion cooperating with the casing to define an exhaust chamber for air discharged through the discharge ports, a cylindrical portion at the other end of smaller diameter than the sleeve portion adapted to encircle the tubular casing to define a restricting longitudinally disposed exhaust passage from the exhaust chamber, a neck portion extending from said cylindrical member adjacent to said cylindrical portion, and a restricting discharge opening in said neck portion extending in a peripheral direction around a portion of the circumference of said neck portion, said discharge opening being adapted to exhaust to atmosphere in an outward and radial direction discharged air flowing through said exhaust passage from said exhaust chamher; and a capping member engageable with the neck portion of said cylindrical member and cooperating with the body of the tool substantially in sealed relation to clamp said capping member and cylindrical member on the tool.

5. In pneumatic tools of the type described having a casing, an operating chamber within said casing, an air discharge means from said operating chamber, and an air driven rotary member operable within said operating chamber: means for mufliing air discharged through said air discharge means from said operating chamber comprising an inner chamber adapted to receive air discharged through said air discharge means, an outer chamber adapted to receive in series such discharged air from said inner chamber, said inner and outer chambers being nonresonant with respect to each other and said outer chamher being disposed in surrounding relationship with respect to at least a portion of said inner chamber, and air discharge means adapted to exhaust to atmosphere the discharged air from said outer chamber including a iongitudinaliy disposed circumferential air-passage means communicating with said outer chamber and an air exhaust port communicating with said circumferential airpassage means and so disposed with respect thereto that References Cited in the file of this patent iJifliTED STATES FATENTS Schmid June 30, 1953 

